The present disclosure relates to a secondary battery, a battery unit, and a battery module, and more particularly, to a secondary battery, a battery unit, and a battery module that have a large current charge and discharge characteristic.
In recent years, a portable electronic apparatus such as a camera-integrated VTR (Video Tape Recorder), a cellular phone, and a notebook PC have become wide spread and weight reduction of such an apparatus has been attempted. With respect to batteries, especially, secondary batteries, which are used as a portable power source of such an electronic apparatus, research and development have been actively performed in order to improve an energy density thereof.
Among secondary batteries using nonaqueous electrolytic solution, in a lithium ion secondary battery, a large energy density may be obtained, compared to a lead battery and a nickel-cadmium battery that are aqueous electrolytic solution secondary batteries in the related art, such that a market has growing significantly. Particularly, recently, a light weight characteristic and a high energy density characteristic of the lithium ion secondary battery are suitable for an electric tool, an electric automobile or a hybrid electric automobile, and an electric assisted bicycle, such that an increase in size and a high output of the secondary battery has been energetically reviewed for the application to such a vehicle.
A nonaqueous based secondary battery represented by a lithium ion secondary battery includes a plurality of positive electrodes and negative electrodes with separators interposed therebetween, and a tab connected to each of the positive electrodes and the negative electrodes. Commonly, the tab, and a positive electrode terminal (negative electrode terminal) interposed between the tab and the positive electrode (negative electrode) have a width thinner than that of the positive electrode (negative electrode) (Japanese Patent Unexamined Patent Application Publication No. 2003-178747).